In various devices including a vehicle, a fail-safe control is performed, for the prioritizing the safety of the device at a device failure time. For example, a control unit in a vehicle that is described in a patent document, JP 2014-105680 A (patent documents 1) listed below performs a fail-safe control by (i) moving the variable valve operation mechanism to move toward a retarded side for positioning the mechanism to a preset position and (ii) using a signal from a cam-position sensor instead of a signal from a crank position sensor when the crank position sensor fails.
Thereby, at the device failure time, a sudden discontinuation of an engine control is prevented, and the user of such device in the vehicle is protected from an accident.
However, the fail-safe control is a safety measure of a post-failure timing, and does not control, or prevent, the failure itself. Further, the energy and resource saving movement in recent years is obliging device makers to manufacture less-failing and high-reliability products (i.e., an Electronic Control Unit (ECU)).